Sept. 20: Obama’s Convention Bounce May Not Be Receding

By NATE SILVER

President Obama’s position inched forward in the FiveThirtyEight forecast on Thursday. His chances of winning the Electoral College are 76.1 percent, according to the forecast, up from 75.2 percent on Wednesday. Mr. Obama’s projected margin of victory in the national popular vote also increased slightly, to 3.4 percentage points.

By and large, the story that Thursday’s polls told was the same one as on Wednesday. Mr. Obama continues to get very strong results in state polls that use industry-standard methodology, meaning that they use live interviews and place calls to mobile phones along with landlines.

In the 10 states that have generally been ranked the highest on our tipping-point list — Ohio, Virginia, Florida, Wisconsin, Colorado, Nevada, Iowa, Pennsylvania, New Hampshire and Michigan — there have been 21 such polls since the Democratic convention ended. Mr. Obama has led in all 21 of these surveys — and usually by clear margins. On average, he has held a six-point lead in these surveys, and he has had close to 50 percent of the vote in them.

Mr. Obama’s results have been more varied among polling firms that use different methodologies. A series of polls in eleven swing states, released on Thursday by the online firm YouGov, were fairly strong for Mr. Obama, putting him ahead among likely voters in all of the states except North Carolina.